The present invention relates to a cover gasket used in a hard disc apparatus.
Conventionally, there has been known a cover gasket 1 for a hard disc apparatus structured, as shown in FIG. 16, such that a rubber 3 corresponding to a sealing gasket is combined with a top cover 2 of the hard disc, and as means for combining the cover 2 and the rubber 3, there can be listed up a structure in which the rubber 3 is integrally molded with the cover 2, a structure in which the rubber 3 having a stainless core metal inserted therein is used and is laid on the cover 2, a structure in which a foamed urethane or a liquid rubber is applied to the cover 2 and cured, a structure in which the cover 2 and the rubber 3 are bonded by using an adhesive agent at a later stage, or the like.
Among them, in the case that the cover 2 and the rubber 3 are bonded later by using the adhesive agent, there is a problem of an inferior bonding due to running out of the adhesive agent.
A mechanism by which running out of adhesive agent and peeling off of the rubber 3 are generated is as follows.
That is, in the case that the cover 2 and the rubber 3 are later bonded by using the adhesive agent (not shown) as shown in FIG. 17, the adhesive agent is applied onto a bonding surface 3a of the rubber 3 and the cover 2 and the rubber 3 are set to a bonding jig 11, thereafter heating and bonding are executed while applying a load P from above (the side of an upper jig 12) as shown in FIG. 18. At this time, in the case that a magnitude of the load P is too great, the rubber 3 is strongly pressed against a lower jig 13 and an excessive force P1 is generated in the outward direction. Accordingly, the adhesive agent 4 applied to the bonding surface 3a of the rubber 3 is forced out, whereby the running out of adhesive agent is caused. Further, since a bonding film interposed between the cover 2 and the rubber 3 becomes accordingly thin, a reduction of bonding force is generated. Further, since the rubber 3 is elastically returned at a time of taking out the top cover 2 from the jig 11, a shear stress P2 is generated in the reverse direction to that at the bonding time as shown in FIG. 19, whereby peeling off of the rubber 3 is caused.
The magnitude of load P, that is, the pressing force of the bonding portion is controlled so that running out of the adhesive agent 4 as mentioned above is not generated and the bonding film does not become thin, and a carrier 14 (refer to FIG. 16) is provided in the jig 11 so as not to press the rubber 3 too much.
However, when a flatness of the bonding portion in the cover 2 is inferior, a great pressing force is required for bonding all the surface of the bonding portion, and even when the carrier 14 is provided in the jig 11, running out of the adhesive agent 4 becomes much due to a partial warp of the cover 2, or the film thickness of the adhesive agent 4 becomes thin. The cover 2 is formed by a press molding, and particularly, in the case of press forming the cover 2 by using a stainless sheet or the like, since a spring back is generated after pressing, it is hard to make the flatness good enough to obtain a good bonding.
Further, when applying the adhesive agent 4 to the bonding surfaces, thereafter sticking the bonding surfaces and putting them on a hot plate in a pressing state, the adhesive agent 4 kept between the bonding surfaces due to a balance of the pressing force and a surface tension of the adhesive agent 4 looses the surface tension in accordance with an increase of temperature, the balance is lost at a certain temperature, and the adhesive agent 4 is pressed out from the bonding surface. At this time, since the adhesive agent 4 is pressed out from a portion having a weak balance first, and a viscosity of the adhesive agent 4 is reduced due to the temperature increase, the adhesive agent is pressed out in such a manner as to run out irregularly from a plurality of portions instead of being pressed out uniformly from a whole of the outer periphery of the bonding surface. Accordingly, as a result, a state after running out becomes to be in a shape in which the adhesive agent 4 runs out zigzagedly from both sides of the rubber 3 like as legs of a scolopendra as shown in a model view in FIG. 20.
Further, a cover gasket in which the cover and the rubber are later bonded by using the adhesive agent is described in Japanese Patent publication No. 2517797, however, the prior art described in this publication is structured such as to run out the adhesive agent and to coat and fix rubber burrs by running out of adhesive agent, that is, running out of the adhesive agent is positively accepted.
The present invention is made by taking the above points into consideration, and an object of the present invention is to provide a cover gasket for a hard disc apparatus in which a cover and a rubber are later bonded by using an adhesive agent, wherein it is possible to prevent running out of an adhesive agent and peeling off of rubber as much as possible.
In order to achieve the object mentioned above, in accordance with a first aspect of the present invention, there is provided a cover gasket for a hard disc apparatus in which a cover and a rubber are later bonded by using an adhesive agent, characterized in that a recess portion for storing the adhesive agent is provided on a bonding surface of the cover or the rubber.
Further, in accordance with a second aspect of the present invention, there is provided a cover gasket as recited in the first aspect mentioned above, characterized in that the recess portion is provided in the center in the width direction of the bonding surface of the rubber.
Further, in accordance with a third aspect of the present invention, there is provided a cover gasket as recited in the first aspect mentioned above, characterized in that the recess portion is provided in the end portions in the width direction of the bonding surface of the rubber.
When the recess portion for storing the adhesive agent is provided on the bonding surface of the cover or the rubber as in the cover gasket in accordance with the first aspect of the present invention provided with the structure mentioned above, the adhesive agent is stored in the recess portion even in the case a pressing force at a time of bonding is large, so that it is possible to restrict running out of the adhesive agent to the minimum. Further, since a bonding film thickness becomes thicker by a part of adhesive agent being stored in the recess portion, it is possible to reinforce a bonding force. In the case of the recess portion is provided on the bonding surface of the rubber, it may be provided in the center in the width direction of the bonding surface as described in the second aspect, or it may be provided in the end portion in the width direction as described in the third aspect. In the latter case, the recess portions also open to side surfaces of the rubber.
In this case, the later bonding means bonding the cover and the rubber after forming each of them in a product shape independently.